Published 4:00 am, Thursday, March 23, 2000

2000-03-23 04:00:00 PDT Redding -- In an odd chemical fluke that has astonished scientists, the world's most acidic water has been found deep inside the polluted remnants of an abandoned mine just west of this Shasta County city.

Already ranked among the worst pollution sites in the country, the vast underground web of mining operations at Iron Mountain, a federal Superfund cleanup site, now has a dubious new claim to fame.

"It's the world's worst water," said Charles Alpers, a research chemist at the U.S. Geological Survey who has been sampling Iron Mountain runoff since the early 1970s.

Latest Living videos

But he and other scientists insisted that the water posed no threat to human health because it is found in tiny quantities, is safely diluted and scrubbed clean before it reaches the tributaries of the Sacramento River downstream, the main source of drinking water for Redding.

The acidic water, they say, is more a scientific curiosity.

Alpers and colleagues at the Geological Survey and the University of Waterloo in Ontario, Canada, first discovered the rare "metal-acid" superwater in field trips in 1990 and 1991. It took them until now to devise proper tests to figure out just what they had -- and to get other scientists to believe their results.

The Iron Mountain water was so contaminated with runoff from abandoned sulfur mines and other extractive industries that conventional chemical measures no longer worked.

The standard gauge of acidity known as pH, for example, ordinarily runs from 0 to 14, where zero is considered the strongest acid, 7 is neutral and 14 is the strongest base.

At Iron Mountain, a sophisticated series of chemical tests showed some drip-water samples had pH values well below zero -- literally off the charts.

The most acidic water sample of all -- and the current record-holder for an acid found outside a laboratory in a natural setting -- tested at a negative 3.6 pH.

It came from what the scientists described as a truly hellish underground world that Dante could scarcely have imagined,

Mining of sulfide ore was conducted at Iron Mountain from the 1860s until the 1960s. The ore was used to make sulfur for Bay Area oil refineries and to make fertilizer. Copper and precious metals also were mined intermittently.

Now the abandoned mine consists of gigantic human-carved chambers with ceilings up to 20 stories high, studded with exotic blue- green mineral formations. Crumbling rock walls drip with acids stronger than those found in a car battery.

Air temperatures in the buried mine pit where the worst water bubbled forth were heated to above 120 degrees Fahrenheit by the chemical reactions of sulfates encountering water and oxygen. Random rock falls were a constant worry.

FINDINGS SHOCKING

Alpers and his colleagues recently published their findings in the journal Environmental Science and Technology. An earlier version of the report was rejected by another leading scientific journal, whose editors "could not believe our results," Alpers said.

He and toxic-cleanup managers for the U.S. Environmental Protection Agency led a tour of the Iron Mountain cleanup site for reporters yesterday.

Officials insisted that the cleanup efforts, which have been under way since 1994, have made a dramatic dent in the Iron Mountain runoff problem, which they said has been almost completely contained.

Already, about 80 percent of the dissolved metals such as zinc, copper and cadmium, which otherwise would be gushing out in the spring runoff and into tributaries of the Sacramento River, are being diverted into eight or nine miles of specially lined acid-resistant pipes, costing $1 million a mile, equipped with automatic sensors to detect leaks.

The pipes deliver the hellish water, in which nothing but a few rare acid-loving microbes can live, into settling tanks, chemical vats and a big high-density sludge-making plant.

ACIDS NEUTRALIZED

Before the effluent is finally released into the river, all the acids are neutralized with several truckloads of hydrated lime delivered daily. The reddish-brown sludge, nearly solid, is hauled up to a plastic double-lined pit left over from the mining operations. The pit, now 150 feet deep, still has enough room for a couple hundred more years of waste containment.

Since the first studies of the pollution problem began in early 1980s, the cleanup has cost $210 million, including $65 million from the EPA and $145 million from the chemical company Rhone Poulenc, corporate successor of the big mine operators.

The EPA and its contractors now are expanding the effort with a dam and other new facilities on a stream called Slickrock Creek, planned to be ready for operation next fall.

The Slickrock runoff accounts for about two-thirds of all the remaining pollution coming off the mountain. Once the new facilities are operating next year, about 95 percent of Iron Mountain's pollution problem will have been essentially solved, Sugarek said.

"This is a success story," he proclaimed, even if it was hard to tell from the huge eroded mounds of arsenic-laced gold-mining refuse just in front of where he stood.

Officials said the acidic Iron Mountain drain water, which can carry far higher concentrations of metals than ordinary water, pose no direct threat to human health even though Redding draws its drinking water from the Sacramento.

Metals such as copper and zinc are considered nutrients for humans, but they can be deadly toxics for fish, clogging their gills. Horrific fish kills, with hundreds of thousands of dead fish floating to shore, had once been a routine occurence downhill from Iron Mountain. But no significant die-offs have been noted since the Superfund cleanup got under way, Sugarek said.

Yesterday's press tour of Iron Mountain stopped just outside the portal of Richmond Mine, inside which the "hottest" acids were found. Cleanup managers said safety rules required a week's training before any civilians could be let in for a glimpse.

Latest from the SFGATE homepage:

Click below for the top news from around the Bay Area and beyond. Sign up for our newsletters to be the first to learn about breaking news and more. Go to 'Sign In' and 'Manage Profile' at the top of the page.